Computer Upgrade

Hi,
What can I do to my computer to help it run Particle Illusion better? When I place certain emitters on the stage they slow down -they don't run in real time. Hard to tell what the finished product will look like.
I have : 3200+ AMD/Athlon XP Processor; NVIDIA GEforce fx5200 graphics card (this is the most I could get because of a 250 watt power supply); 1 GB RAM (I think I can go to 2GB). Other than purchasing a higher end workstation is there anything else I can do? Thanks for any suggestions.